1. Field of the Invention
The present invention relates to a touch panel, and more particularly, to a touch panel capable of reducing influence of noise so as to detect a touch position with high precision.
2. Description of the Related Art
A display device which includes a device for inputting information by a touch operation (contact press operation; hereinafter, simply referred to as touch) onto a display screen with the use of a user's finger or a pen (hereinafter, the device is referred to also as touch sensor or touch panel) is used for mobile electronic devices such as a PDA and a mobile terminal, various home electric appliances, an automated teller machine, and other such devices. As the touch panel, there are known a resistive type touch panel that detects a change in resistance at a touched portion, a capacitance type touch panel that detects a change in capacitance, and an optical sensor type touch panel that detects a change in light intensity.
The capacitance type touch panel includes a plurality of detection electrodes extending in a vertical direction (X electrodes) and a plurality of detection electrodes extending in a horizontal direction (Y electrodes), and an input processing portion detects interelectrode capacitances at respective intersections of the X electrodes and the Y electrodes arranged in a matrix. When a conductor such as a finger makes contact with the front surface of the touch panel, the capacitance of an electrode placed at the contact position increases. The input processing portion detects the change in capacitance, and calculates input coordinates based on a signal of the capacitance change detected at each electrode.